Energy and angular differential cross sections for K + NO2 charge transfer reactions

Doubly differential cross sections, in energy and angle, are reported for the electron transfer reaction between potassium and nitrogen dioxide in a crossed beam apparatus at relative collision energies between 2.7 and 30.8 eV. The formation of NO^?₂ in its ground ¹A₁ and excited ³B₁ state has been observed. Theoretical consideration of these processes indicates that bond bending during the collision has a stronger influence on ion-pair formation than bond stretching. At the lower collision energies most of the excess energy is converted into internal energy of NO^?₂.     

Diels-alder reactions of substituted maleic anhydrides with 1-vinylcoclohexane: Stereospecific formation of a bicyclic intermediate useful for syntheses of clerodane diterpenes

The Diels-Alder reaction of 1-vinylcyclohexene with aconitic anhydride gives the adduct 5b which has the reversed stereochemistry of that predicted by Alder's endo rule. On the other hand, reactions with chloromethylmaleic anhydride and citraconic anhydride afford endo-adducts 23 and 24, respectively. Adduct 23 has the appropriate stereochemistry and functionality for the syntheses of clerodane and related diterpenes.     

Pavoninins,shark-repelling and ichthyotoxic steroid n-acetylglucosaminides from the defense secretion of the sole pardachirus pavoninus (soleidae)

Six steroid itN-acctylglueosaminides, pavoninins-1 to -6, have been isolated from the defense secretion of the sole P. pavoninus guided by ichthyotoxicity and hemolytic activity, and their structures determined to be 1–6 by spcctroscopic studies and chemical correlations. The pavoninins are considered to be the factors responsible for the repellent property of the sole against predatory fishes.     

Synthetic studies on terpenic compounds—XI : Stereospecific total synthesis of portulal,

A stereospecific total synthesis of portulal 1 has been accomplished starting from the Diels-Alder adduct 2 from chloromethylmaleic anhydride and 1-vinylcyclohexene. Firstly 2 was converted by an efficient sequence of reactions to perhydroazulenoid lactone 5, which possesses the correct relative configuration with respect to three chiral centers out of the four present in 1. The fourth chiral center at C-6 was introduced stereospecifically together with the one-carbon substituent at C-4 by the ring formation between C-4 and C-6, and its cleavage to give an exomethylene lactone 35. At this stage the stereochemical validity of the crucial intermediate 35 was confirmed by chemical correlation with the hydroxy lactone 37 which was derived from natural 1 through a systematic degradation. Then 35 was transformed to 37 and the synthesis continued further by using 37 as a relay compound to afford 1.     

Microwave spectrum and dipole moment of 1,2,3,4-tetra-fluorobenzene

The microwave spectrum of the ground state of 1,2,3,4-tetrafluorobenzene has been measured in the range 7 to 25 GHz. A possible structure of the molecule is discussed. The rotational constants obtained are (in MHz): A = 2090.711 ± 0.012, B = 1196.257 ± 0.014, C = 760.880 ± 0.005. The observed inertial defect, Δ = 0.010 amu Ų, confirms the planar structure. A dipole moment of 2.42 ± 0.05 Debye was determined.     

Classification of monosubstituted phenyl rings by branching tree methods using infrared and raman peak heights

A branching tree scheme is proposed and evaluated for classifying monosubstituted benzenes by the structure of the part of a substituent which lies near the phenyl ring. A large group having the same atom attached to the phenyl ring is divided into subgroups having a more highly defined structure. Each subgroup is then further divided into still smaller subgroups having still more highly defined structures. Combined sets of infrared and Raman peak heights for bands characteristic of the phenyl ring vibrations are used as pattern vectors. A statistical linear discriminant method is used to correlate the peak heights of groups having similar near-the-ring structure. The stepwise and overall success rates are given for each level of classification.     

The crystal structure of bicyclo [3.3.3]undecane-1,5-diol and the conformation of bicyclo[3.3.3]undecane (manxane)

The crystal structure of bicyclo [3.3.3]undecane-1,5-diol has been determined. It is monoclinic, P2₁/c, a = 12.99(2), b = 14.16(2), c = 12.50(1)A,β = 112.42(2)°, with two independent molecules in the asymmetric unit. One of these is disordered, but the other has almost exact C_3h symmetry and its conformation and precise molecular geometry agree well with previous calculations by molecular mechanics. The molecule shows considerable angle strain, having bridge angles in the range 118–121°     

A study of porphyrin analogues—III : Syntheses,enzyme interactions and self-aggregation of new models for types I,III and IX porphyrins

Three new porphyrin free bases have been synthesised and their interaction with the mitochondrial enzyme Ferrochelatase has been studied. The model compound for type IX porphyrins is the best substrate for Ferrochelatase so far studied, whereas the model compound for type I porphyrins is the only compound of this type to act as a substrate for this enzyme. The model compound for type III porphyrins is not a substrate, but does act as a competitive inhibitor.The ¹H NMR spectra of the new compounds in their dimethyl diester form differ substantially from the spectra of their zinc(II)bis-pyrrolidine adducts, showing that aggregation is taking place. The results for the α-meso and γ-meso protons in particular are unusual and indicate that aggregation is taking place anomalously, with electronic effects dominating steric effects.     

Differential determination of arsenic(III) and arsenic(V), and antimony(III) and antimony(V) by hydride generation-atomic absorption spectrophotometry,and its application to the determination of these species in sea water

A method is described for the differential determination of As(III) and As(V). and Sb(III) and Sb(V) by hydride generation-atomic absorption spectrophotometry with hydrogen-nitrogen flame using sodium borohydride solution as a reductant. For the determination of As(III) and Sb(III), most of the elements, other than Ag⁺, Cu²⁺, Sn²⁺, Se⁴⁺ and Te⁴⁺, do not interfere in an at least 30,000 fold excess with respect to As(III) or Sb(III). This method was applied to the determination of these species in sea water and it was found that a sample size of only 100 ml is enough to determine them with a precision of 1.5–2.5%. Analytical results for surface sea water of Hiroshima Bay were 0.72 μgl^?1, 0.27 μgl^?1 and 0.22 μgl^?1 for As(total), As(III) and Sb(total), respectively, but Sb(III) was not detected in the present sample. The effect of acidification on storage was also examined.     

Supernucleophiles—II: Orbital interactions and nucleophilicity

The role of adjacent lone pair centers upon the nucleophilic reactivity of various amines with p-nitrophenyl acetate has been studied. The kinetics of appropriately substituted hydroxy- and methoxyamines, as well as unsubstituted analogs are presented. The effect of orbital orientation was evaluated theoretically for 1-aminoethanol using CNDO/2. The results of the theoretical study imply a small through-bond and an even smaller through-space lone pair interaction. Kinetically, rate enhancements resulting from such interactions are not observed.     

Synthesis of 2,3,4-trideoxy-4-c-(phenylphosphinyl)-dl-glycero-pentofuranose and its 1,5-diacetate

Synthesis of 2,3,4-trideoxy-4-C-(phenylphosphinyl)-dl-glycero-pentofuranose (11) starting from 2-furanmethanol was successful. The reaction of methyl 2,3-dideoxy-(1S)-dl-pentopyranosid-4-ulose 4-(p-toluenesulfonylhydrazone) with methyl phenylphosphonite gave methyl (4RS)-2,3,4-trideoxy-4-C-[(methoxy)phenylphosphinyl]-4-C-(p-toluenesulfonylhydrazino)-(1S)-dl-pentopyranoside (7), which on treatment with sodium borohydride afforded methyl 2,3,4-trideoxy-4-C-[(methoxy)phenylphosphinyl]-(1S)-dl-glycero-pentopyranoside (9). Treatment of compound 9 with SDMA followed by hydrolysis and treatment with acetic anhydride-pyridine afforded 1,5-diacetate 12 of compound 11.     

Reactions of water with carbon and ethylene over illuminated pt/tio2

The room temperature reaction between gas phase water and active carbon to form carbon dioxide and hydrogen on a platinized titanium dioxide catalyst, illuminated with band gap radiation, is reported. Using the same catalyst system, ethylene is converted to ethane, carbon dioxide, hydrogen and a small amount of methane.     

On the contributions of resonance,hybridization and nonbonded interactions to the structure of butadiene

A recent ab initio molecular orbital calculation on butadiene has been interpreted by Skaarup, Boggs and Skancke as indicating that the shortness of the central C-C bond is due primarily to hybridization. Resonance was considered to make a minor contribution and nonbonded interactions were judged to be unimportant. Unfortunately, this analysis failed to take into account the crucial role of geminal nonbonded interactions, and the calculations were, accordingly, not designed to discriminate between the hybridization and nonbonded models. A more direct investigation of intramolecular nonbonded interactions based on ab initio computations has been earned out on other systems, however, providing evidence that the effects of nonbonded contributions are substantial.     

Synthesis of mevalonolactone (hiochic acid lactone) employing asymmetric epoxidation as the key-step

(R)( — )-Mevalonolactone (hiochic acid lactone)of 91–93%e.e. was synthesized from an achiral starting material employing the Sharpless asymmetric epoxidation as the key-step.     

Structure of citreoviridin,a mycotoxin produced by penicillium citreo-viride molded on rice

Structure of citreoviridin, a “yellowed rice toxin” produced by P. citreo-viride molded on rice, was determined as 1b.     

Molecular emission cavity analysis13-a new flame analytical technique : Part II.The determination of selenium and tellurium

The determination of 0.4–4 μg of selenium by molecular emission cavity analysis is described. Selenium in organic compounds is determined after oxygen flask combustion. Metal ion interferences are eliminated by reduction of selenium to the element, filtration onto a glass-fibre paper, and direct incorporation of the filter into the cavity. Applications to the determination of selenium in inorganic and organic compounds are described. The determination of μg-amounts of tellurium is also outlined.     

Monte Carlo based electronic structure techniques: analysis and applications

Monte Carlo based variational electronic structure techniques are examined. The nature of the convergence of such methods, associated extrapolation methods and techniques for wavefunction optimization are discussed. These techniques are illustrated with an application to the H⁺₃ system. Compact and accurate correlated wavefunctions for this system are reported.     

Cationic di- and mono-carbonyl complexes of manganese(I)

The complexes fac-O₃ClOMn(CO)₃(NN) (NN = 1,10-phenantroline (phen) or 2,2'bipyridine (bipy)) react with an excess of the ligands L [L = P(OR)₃ or P(OR)₂Ph, R = Me or Et] in refluxing ethanol to give cis-trans-[Mn(CO)₂-(NN)L₂]ClO₄, or the more highly substituted [Mn(CO)(NN)L₃]ClO₄ if the reaction is carried out under UV irradiation. Carbonylation at normal pressure of the latter complexes results in the formation of cis-cis-[Mn(CO)₂(NN)L₂]ClO₄, which undergo isomerization to the cis-trans isomer when heated in acetone.Treatment of fac-O₃ClOMn(CO)₃(dpe) (dpe = 1,2-bis(diphenylphosphino)-ethane] with bipy or phen in refluxing ethanol gives the corresponding cis-[Mn(CO)₂(NN)(dpe)]ClO₄ complexes, and irradiation of these with UV in the presence of an excess of P(OR)₃ (R = Ph, Et or Me) gives the monocarbonyls [Mn(CO)(NN)(dpe)L]ClO₄.     

Electrolyte—formamide interactions studied by raman spectroscopy

The effects of dissolved electrolytes on the structure of liquid formamide have been investigated by Raman spectroscopy. The spectral features are dependent on the concentration and nature of the dissolved electrolyte and are discussed in terms of direct electrolyte formamide interactions. Two vN—H bands, arising from ion—formamide species, have been observed superimposed on the spectrum of residual liquid formamide. The results lend further support to the interaction model for electrolytes in liquid formamide previously proposed by us on the basis of nuclear magnetic resonance and infrared spectral data.     

Mixed ligand complexes of ruthenium(III), rhodium(III) and iridium(III) with dipicolinic acid and some monobasic bidentate nitrogen,oxygen donor ligands

The trivalent ruthenium, rhodium and iridium complexes of dipicolinic acid and its mixed ligand complexes with several nitrogen, oxygen donor molecules, of types: Na[M(dipic)₂]·2H₂O and [M(dipic)(N-O)]·nH₂O (where M = Ru(III), Rh(III) or Ir(III); dipicH₂ = dipicolinic acid; NOH represents different nitrogen, oxygen donor molecules, viz., picolinic acid, nicotinic acid, isonicotinic acid, glycine, aminophenol, o- or p-aminobenzoic acid), have been synthesized and characterised on the basis of elemental analyses, electrical conductance, magnetic susceptibility measurements and spectral (electronic and infrared) data. The parent dipicolinic acid complexes are found to have a six-coordinate pseudooctahedral structure, whereas for mixed ligand complexes, a polymeric six-coordinate structure has been assigned. Various ligand field and nephelauxetic parameters have also been evaluated.